FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] This gene encodes a member of the p55-like subfamily of the membrane-associated guanylate kinase (MAGUK) gene superfamily. The encoded protein participates in the polarization of differentiating cells, has been shown to regulate myelinating Schwann cells (PMID: 20237282), and is one of the components of the Crumbs complex in the retina. Mice which express lower levels of the orthologous protein have retinal degeneration and impaired vision (PMID: 22114289). Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Feb 2012] PHENOTYPE: Mice homozygous for a floxed allele activated in cortical neuron exhibit loss of cortex neurons due to premature differentiation and increased apoptosis. These mice also exhibit behavioral defects but are otherwise viable and fertile. Heterozygous mice exhibit an intermediate phenotype. [provided by MGI curators]